A standard single-lever valve, as for instance is typically incorporated in a faucet, has an operating lever that is shifted according to one degree of freedom, normally pivotally up and down, to control the volume of flow through the valve, and according to a second degree of freedom, normally pivotally from side to side, to control the mix of hot and cold water passed through the valve. Thus the user can easily set the volume and temperature.
In U.S. Pat. No. 4,688,277 of Kakinoki a faucet assembly is described which has, in addition to the above-described mechanical control system, a servoactuator that allows the valve to be opened when a proximity detector senses the approach of an object, typically the user's hands under the faucet. Thus this system has a proximity-sensing servo system that can operate the mechanical system. This arrangement is highly effective but very complex and expensive.